Field of the Invention
The present invention relates to a position detection apparatus, a position detection method, an imprint apparatus, and a method of manufacturing an article.
Description of the Related Art
An imprint technique is a technique capable of forming nano-scale fine patterns, and is proposed as one of the mass-production nanolithography techniques for semiconductor devices and magnetic storage media. An imprint apparatus using an imprint technique cures a resin (imprint material) on a substrate while a mold on which patterns are formed is in contact with the resin and then separates the mold from the cured resin, thereby forming the patterns on the substrate. The imprint apparatus generally uses, as a resin curing method, a photo-curing method of curing a resin on a substrate by irradiating the resin with light such as ultraviolet light.
The imprint apparatus needs to accurately align a mold with a substrate when contacting the mold with a resin on the substrate. For example, as an alignment scheme for a mold and a substrate, a die-by-die alignment scheme is used. The die-by-die alignment scheme is a scheme of performing alignment by detecting a mark formed on each shot region on a substrate and a corresponding mark on a mold. Such techniques associated with the alignment between a mold and a substrate has been proposed in U.S. Pat. No. 7,292,326 and Japanese Patent Laid-Open No. 2013-030757.
The specification of U.S. Pat. No. 7,292,326 has proposed an imprint apparatus including a mark detection mechanism for detecting marks used for the alignment between a mold and a substrate. According to the specification of U.S. Pat. No. 7,292,326, a mold and a substrate are respectively provided with diffraction gratings as marks used for the alignment between the mold and the substrate. A diffraction grating on the mold side is a one that has a period in the measurement direction. A diffraction grating on the substrate side is a one with a checkerboard pattern that has periods in both the measurement direction and a direction (non-measurement direction) perpendicular to the measurement direction. The mark detection mechanism detects the moire caused by the overlap between a diffraction grating on the substrate side and a diffraction grating on the mold side. The mark detection mechanism includes an illumination optical system which illuminates diffraction gratings and a detection optical system which detects diffracted light from the diffraction gratings. Both the systems are arranged at tilts from a direction perpendicular to a mold and a substrate to non-measurement directions. In other words, the illumination optical system is configured to perform oblique incident illumination on a diffraction grating from a non-measurement direction. Light obliquely entering a diffraction grating on the substrate side is diffracted in a non-measurement direction by the diffraction grating, and is detected by the detection optical system. The detection optical system is arranged in a non-measurement direction to detect only a single diffracted light beam other than 0th-order light. In addition, Japanese Patent Laid-Open No. 2013-030757 has proposed a technique of forming a plurality of poles in the pupil plane of the illumination optical system and measuring the relative positions between a mold and a substrate in a plurality of directions.
According to the related art, however, strong diffracted light or scattered light is generated from ends of a diffraction grating on the mold side and of a diffraction grating on the substrate side (two ends of the patterns of each diffraction grating), and their influences are reflected in the detection signals obtained by the mark detection mechanism, resulting in the occurrence of “deception” (errors). As a result, the alignment accuracy (overlap accuracy) between molds and substrates deteriorates, leading to pattern transfer failures (product failures).